/* Ppmd8.c -- PPMdI codec
   2010-03-24 : Igor Pavlov : Public domain
   This code is based on PPMd var.I (2002): Dmitry Shkarin : Public domain */

#include "Types.h"

#include "Ppmd8.h"

const Byte PPMD8_kExpEscape[16] = { 25, 14, 9, 7, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
static const UInt16 kInitBinEsc[] = { 0x3CDD, 0x1F3F, 0x59BF, 0x48F3, 0x64A1, 0x5ABC, 0x6632, 0x6051 };

#define MAX_FREQ 124
#define UNIT_SIZE 12

#define U2B(nu) ((UInt32)(nu) * UNIT_SIZE)
#define U2I(nu) (p->Units2Indx[(nu) - 1])
#define I2U(indx) (p->Indx2Units[indx])

#ifdef PPMD_32BIT
    #define REF(ptr) (ptr)
#else
    #define REF(ptr) ((UInt32)((Byte*)(ptr) - (p)->Base))
#endif

#define STATS_REF(ptr) ((CPpmd_State_Ref)REF(ptr))

#define CTX(ref) ((CPpmd8_Context*)Ppmd8_GetContext(p, ref))
#define STATS(ctx) Ppmd8_GetStats(p, ctx)
#define ONE_STATE(ctx) Ppmd8Context_OneState(ctx)
#define SUFFIX(ctx) CTX((ctx)->Suffix)

typedef CPpmd8_Context* CTX_PTR;

struct CPpmd8_Node_;

typedef
#ifdef PPMD_32BIT
struct CPpmd8_Node_*
#else
UInt32
#endif
CPpmd8_Node_Ref;

typedef struct CPpmd8_Node_
{
    UInt32 Stamp;
    CPpmd8_Node_Ref Next;
    UInt32 NU;
} CPpmd8_Node;

#ifdef PPMD_32BIT
    #define NODE(ptr) (ptr)
#else
    #define NODE(offs) ((CPpmd8_Node*)(p->Base + (offs)))
#endif

#define EMPTY_NODE 0xFFFFFFFF

void Ppmd8_Construct(CPpmd8* p)
{
    unsigned i, k, m;

    p->Base = 0;

    for (i = 0, k = 0; i < PPMD_NUM_INDEXES; i++)
    {
        unsigned step = (i >= 12 ? 4 : (i >> 2) + 1);
        do
        {
            p->Units2Indx[k++] = (Byte)i;
        }
        while (--step);
        p->Indx2Units[i] = (Byte)k;
    }

    p->NS2BSIndx[0] = (0 << 1);
    p->NS2BSIndx[1] = (1 << 1);
    memset(p->NS2BSIndx + 2, (2 << 1), 9);
    memset(p->NS2BSIndx + 11, (3 << 1), 256 - 11);

    for (i = 0; i < 5; i++)
        p->NS2Indx[i] = (Byte)i;
    for (m = i, k = 1; i < 260; i++)
    {
        p->NS2Indx[i] = (Byte)m;
        if (--k == 0)
            k = (++m) - 4;
    }
}

void Ppmd8_Free(CPpmd8* p, ISzAlloc* alloc)
{
    alloc->Free(alloc, p->Base);
    p->Size = 0;
    p->Base = 0;
}

Bool Ppmd8_Alloc(CPpmd8* p, UInt32 size, ISzAlloc* alloc)
{
    if (p->Base == 0 || p->Size != size)
    {
        Ppmd8_Free(p, alloc);
        p->AlignOffset =
            #ifdef PPMD_32BIT
                (4 - size) & 3;
            #else
            4 - (size & 3);
        #endif
        if ((p->Base = (Byte*)alloc->Alloc(alloc, p->AlignOffset + size)) == 0)
            return False;
        p->Size = size;
    }
    return True;
}

static void InsertNode(CPpmd8* p, void* node, unsigned indx)
{
    ((CPpmd8_Node*)node)->Stamp = EMPTY_NODE;
    ((CPpmd8_Node*)node)->Next = (CPpmd8_Node_Ref)p->FreeList[indx];
    ((CPpmd8_Node*)node)->NU = I2U(indx);
    p->FreeList[indx] = REF(node);
    p->Stamps[indx]++;
}

static void * RemoveNode(CPpmd8* p, unsigned indx)
{
    CPpmd8_Node* node = NODE((CPpmd8_Node_Ref)p->FreeList[indx]);
    p->FreeList[indx] = node->Next;
    p->Stamps[indx]--;
    return node;
}

static void SplitBlock(CPpmd8* p, void* ptr, unsigned oldIndx, unsigned newIndx)
{
    unsigned i, nu = I2U(oldIndx) - I2U(newIndx);
    ptr = (Byte*)ptr + U2B(I2U(newIndx));
    if (I2U(i = U2I(nu)) != nu)
    {
        unsigned k = I2U(--i);
        InsertNode(p, ((Byte*)ptr) + U2B(k), nu - k - 1);
    }
    InsertNode(p, ptr, i);
}

static void GlueFreeBlocks(CPpmd8* p)
{
    CPpmd8_Node_Ref head = 0;
    CPpmd8_Node_Ref* prev = &head;
    unsigned i;

    p->GlueCount = 1 << 13;
    memset(p->Stamps, 0, sizeof(p->Stamps));

    /* Order-0 context is always at top UNIT, so we don't need guard NODE at the end.
       All blocks up to p->LoUnit can be free, so we need guard NODE at LoUnit. */
    if (p->LoUnit != p->HiUnit)
        ((CPpmd8_Node*)p->LoUnit)->Stamp = 0;

    /* Glue free blocks */
    for (i = 0; i < PPMD_NUM_INDEXES; i++)
    {
        CPpmd8_Node_Ref next = (CPpmd8_Node_Ref)p->FreeList[i];
        p->FreeList[i] = 0;
        while (next != 0)
        {
            CPpmd8_Node* node = NODE(next);
            if (node->NU != 0)
            {
                CPpmd8_Node* node2;
                *prev = next;
                prev = &(node->Next);
                while ((node2 = node + node->NU)->Stamp == EMPTY_NODE)
                {
                    node->NU += node2->NU;
                    node2->NU = 0;
                }
            }
            next = node->Next;
        }
    }
    *prev = 0;

    /* Fill lists of free blocks */
    while (head != 0)
    {
        CPpmd8_Node* node = NODE(head);
        unsigned nu;
        head = node->Next;
        nu = node->NU;
        if (nu == 0)
            continue;
        for (; nu > 128; nu -= 128, node += 128)
            InsertNode(p, node, PPMD_NUM_INDEXES - 1);
        if (I2U(i = U2I(nu)) != nu)
        {
            unsigned k = I2U(--i);
            InsertNode(p, node + k, nu - k - 1);
        }
        InsertNode(p, node, i);
    }
}

static void * AllocUnitsRare(CPpmd8* p, unsigned indx)
{
    unsigned i;
    void* retVal;
    if (p->GlueCount == 0)
    {
        GlueFreeBlocks(p);
        if (p->FreeList[indx] != 0)
            return RemoveNode(p, indx);
    }
    i = indx;
    do
    {
        if (++i == PPMD_NUM_INDEXES)
        {
            UInt32 numBytes = U2B(I2U(indx));
            p->GlueCount--;
            return ((UInt32)(p->UnitsStart - p->Text) > numBytes) ? (p->UnitsStart -= numBytes) : (NULL);
        }
    }
    while (p->FreeList[i] == 0);
    retVal = RemoveNode(p, i);
    SplitBlock(p, retVal, i, indx);
    return retVal;
}

static void * AllocUnits(CPpmd8* p, unsigned indx)
{
    UInt32 numBytes;
    if (p->FreeList[indx] != 0)
        return RemoveNode(p, indx);
    numBytes = U2B(I2U(indx));
    if (numBytes <= (UInt32)(p->HiUnit - p->LoUnit))
    {
        void* retVal = p->LoUnit;
        p->LoUnit += numBytes;
        return retVal;
    }
    return AllocUnitsRare(p, indx);
}

#define MyMem12Cpy(dest, src, num) \
    { UInt32* d = (UInt32*)dest; const UInt32* s = (const UInt32*)src; UInt32 n = num; \
      do { d[0] = s[0]; d[1] = s[1]; d[2] = s[2]; s += 3; d += 3; } while (--n); }

static void * ShrinkUnits(CPpmd8* p, void* oldPtr, unsigned oldNU, unsigned newNU)
{
    unsigned i0 = U2I(oldNU);
    unsigned i1 = U2I(newNU);
    if (i0 == i1)
        return oldPtr;
    if (p->FreeList[i1] != 0)
    {
        void* ptr = RemoveNode(p, i1);
        MyMem12Cpy(ptr, oldPtr, newNU);
        InsertNode(p, oldPtr, i0);
        return ptr;
    }
    SplitBlock(p, oldPtr, i0, i1);
    return oldPtr;
}

static void FreeUnits(CPpmd8* p, void* ptr, unsigned nu)
{
    InsertNode(p, ptr, U2I(nu));
}

static void SpecialFreeUnit(CPpmd8* p, void* ptr)
{
    if ((Byte*)ptr != p->UnitsStart)
        InsertNode(p, ptr, 0);
    else
    {
        #ifdef PPMD8_FREEZE_SUPPORT
        *(UInt32*)ptr = EMPTY_NODE; /* it's used for (Flags == 0xFF) check in RemoveBinContexts */
        #endif
        p->UnitsStart += UNIT_SIZE;
    }
}

static void * MoveUnitsUp(CPpmd8* p, void* oldPtr, unsigned nu)
{
    unsigned indx = U2I(nu);
    void* ptr;
    if ((Byte*)oldPtr > p->UnitsStart + 16 * 1024 || REF(oldPtr) > p->FreeList[indx])
        return oldPtr;
    ptr = RemoveNode(p, indx);
    MyMem12Cpy(ptr, oldPtr, nu);
    if ((Byte*)oldPtr != p->UnitsStart)
        InsertNode(p, oldPtr, indx);
    else
        p->UnitsStart += U2B(I2U(indx));
    return ptr;
}

static void ExpandTextArea(CPpmd8* p)
{
    UInt32 count[PPMD_NUM_INDEXES];
    unsigned i;
    memset(count, 0, sizeof(count));
    if (p->LoUnit != p->HiUnit)
        ((CPpmd8_Node*)p->LoUnit)->Stamp = 0;

    {
        CPpmd8_Node* node = (CPpmd8_Node*)p->UnitsStart;
        for (; node->Stamp == EMPTY_NODE; node += node->NU)
        {
            node->Stamp = 0;
            count[U2I(node->NU)]++;
        }
        p->UnitsStart = (Byte*)node;
    }

    for (i = 0; i < PPMD_NUM_INDEXES; i++)
    {
        CPpmd8_Node_Ref* next = (CPpmd8_Node_Ref*)&p->FreeList[i];
        while (count[i] != 0)
        {
            CPpmd8_Node* node = NODE(*next);
            while (node->Stamp == 0)
            {
                *next = node->Next;
                node = NODE(*next);
                p->Stamps[i]--;
                if (--count[i] == 0)
                    break;
            }
            next = &node->Next;
        }
    }
}

#define SUCCESSOR(p) ((CPpmd_Void_Ref)((p)->SuccessorLow | ((UInt32)(p)->SuccessorHigh << 16)))

static void SetSuccessor(CPpmd_State* p, CPpmd_Void_Ref v)
{
    (p)->SuccessorLow = (UInt16)((UInt32)(v) & 0xFFFF);
    (p)->SuccessorHigh = (UInt16)(((UInt32)(v) >> 16) & 0xFFFF);
}

#define RESET_TEXT(offs) { p->Text = p->Base + p->AlignOffset + (offs); }

static void RestartModel(CPpmd8* p)
{
    unsigned i, k, m, r;

    memset(p->FreeList, 0, sizeof(p->FreeList));
    memset(p->Stamps, 0, sizeof(p->Stamps));
    RESET_TEXT(0);
    p->HiUnit = p->Text + p->Size;
    p->LoUnit = p->UnitsStart = p->HiUnit - p->Size / 8 / UNIT_SIZE * 7 * UNIT_SIZE;
    p->GlueCount = 0;

    p->OrderFall = p->MaxOrder;
    p->RunLength = p->InitRL = -(Int32)((p->MaxOrder < 12) ? p->MaxOrder : 12) - 1;
    p->PrevSuccess = 0;

    p->MinContext = p->MaxContext = (CTX_PTR)(p->HiUnit -= UNIT_SIZE); /* AllocContext(p); */
    p->MinContext->Suffix = 0;
    p->MinContext->NumStats = 255;
    p->MinContext->Flags = 0;
    p->MinContext->SummFreq = 256 + 1;
    p->FoundState = (CPpmd_State*)p->LoUnit; /* AllocUnits(p, PPMD_NUM_INDEXES - 1); */
    p->LoUnit += U2B(256 / 2);
    p->MinContext->Stats = REF(p->FoundState);
    for (i = 0; i < 256; i++)
    {
        CPpmd_State* s = &p->FoundState[i];
        s->Symbol = (Byte)i;
        s->Freq = 1;
        SetSuccessor(s, 0);
    }

    for (i = m = 0; m < 25; m++)
    {
        while (p->NS2Indx[i] == m)
            i++;
        for (k = 0; k < 8; k++)
        {
            UInt16 val = (UInt16)(PPMD_BIN_SCALE - kInitBinEsc[k] / (i + 1));
            UInt16* dest = p->BinSumm[m] + k;
            for (r = 0; r < 64; r += 8)
                dest[r] = val;
        }
    }

    for (i = m = 0; m < 24; m++)
    {
        while (p->NS2Indx[i + 3] == m + 3)
            i++;
        for (k = 0; k < 32; k++)
        {
            CPpmd_See* s = &p->See[m][k];
            s->Summ = (UInt16)((2 * i + 5) << (s->Shift = PPMD_PERIOD_BITS - 4));
            s->Count = 7;
        }
    }
}

void Ppmd8_Init(CPpmd8* p, unsigned maxOrder, unsigned restoreMethod)
{
    p->MaxOrder = maxOrder;
    p->RestoreMethod = restoreMethod;
    RestartModel(p);
    p->DummySee.Shift = PPMD_PERIOD_BITS;
    p->DummySee.Summ = 0; /* unused */
    p->DummySee.Count = 64; /* unused */
}

static void Refresh(CPpmd8* p, CTX_PTR ctx, unsigned oldNU, unsigned scale)
{
    unsigned i = ctx->NumStats, escFreq, sumFreq, flags;
    CPpmd_State* s = (CPpmd_State*)ShrinkUnits(p, STATS(ctx), oldNU, (i + 2) >> 1);
    ctx->Stats = REF(s);
    #ifdef PPMD8_FREEZE_SUPPORT
    /* fixed over Shkarin's code. Fixed code is not compatible with original code for some files in FREEZE mode. */
    scale |= (ctx->SummFreq >= ((UInt32)1 << 15));
    #endif
    flags = (ctx->Flags & (0x10 + 0x04 * scale)) + 0x08 * (s->Symbol >= 0x40);
    escFreq = ctx->SummFreq - s->Freq;
    sumFreq = (s->Freq = (Byte)((s->Freq + scale) >> scale));
    do
    {
        escFreq -= (++s)->Freq;
        sumFreq += (s->Freq = (Byte)((s->Freq + scale) >> scale));
        flags |= 0x08 * (s->Symbol >= 0x40);
    }
    while (--i);
    ctx->SummFreq = (UInt16)(sumFreq + ((escFreq + scale) >> scale));
    ctx->Flags = (Byte)flags;
}

static void SwapStates(CPpmd_State* t1, CPpmd_State* t2)
{
    CPpmd_State tmp = *t1;
    *t1 = *t2;
    *t2 = tmp;
}

static CPpmd_Void_Ref CutOff(CPpmd8* p, CTX_PTR ctx, unsigned order)
{
    int i;
    unsigned tmp;
    CPpmd_State* s;

    if (!ctx->NumStats)
    {
        s = ONE_STATE(ctx);
        if ((Byte*)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart)
        {
            if (order < p->MaxOrder)
                SetSuccessor(s, CutOff(p, CTX(SUCCESSOR(s)), order + 1));
            else
                SetSuccessor(s, 0);
            if (SUCCESSOR(s) || order <= 9) /* O_BOUND */
                return REF(ctx);
        }
        SpecialFreeUnit(p, ctx);
        return 0;
    }

    ctx->Stats = STATS_REF(MoveUnitsUp(p, STATS(ctx), tmp = ((unsigned)ctx->NumStats + 2) >> 1));

    for (s = STATS(ctx) + (i = ctx->NumStats); s >= STATS(ctx); s--)
        if ((Byte*)Ppmd8_GetPtr(p, SUCCESSOR(s)) < p->UnitsStart)
        {
            CPpmd_State* s2 = STATS(ctx) + (i--);
            SetSuccessor(s, 0);
            SwapStates(s, s2);
        }
        else if (order < p->MaxOrder)
            SetSuccessor(s, CutOff(p, CTX(SUCCESSOR(s)), order + 1));
        else
            SetSuccessor(s, 0);

    if (i != ctx->NumStats && order)
    {
        ctx->NumStats = (Byte)i;
        s = STATS(ctx);
        if (i < 0)
        {
            FreeUnits(p, s, tmp);
            SpecialFreeUnit(p, ctx);
            return 0;
        }
        if (i == 0)
        {
            ctx->Flags = (ctx->Flags & 0x10) + 0x08 * (s->Symbol >= 0x40);
            *ONE_STATE(ctx) = *s;
            FreeUnits(p, s, tmp);
            ONE_STATE(ctx)->Freq = (Byte)((unsigned)ONE_STATE(ctx)->Freq + 11) >> 3;
        }
        else
            Refresh(p, ctx, tmp, ctx->SummFreq > 16 * i);
    }
    return REF(ctx);
}

#ifdef PPMD8_FREEZE_SUPPORT
static CPpmd_Void_Ref RemoveBinContexts(CPpmd8* p, CTX_PTR ctx, unsigned order)
{
    CPpmd_State* s;
    if (!ctx->NumStats)
    {
        s = ONE_STATE(ctx);
        if ((Byte*)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart && order < p->MaxOrder)
            SetSuccessor(s, RemoveBinContexts(p, CTX(SUCCESSOR(s)), order + 1));
        else
            SetSuccessor(s, 0);
        /* Suffix context can be removed already, since different (high-order)
           Successors may refer to same context. So we check Flags == 0xFF (Stamp == EMPTY_NODE) */
        if (!SUCCESSOR(s) && (!SUFFIX(ctx)->NumStats || SUFFIX(ctx)->Flags == 0xFF))
        {
            FreeUnits(p, ctx, 1);
            return 0;
        }
        else
            return REF(ctx);
    }

    for (s = STATS(ctx) + ctx->NumStats; s >= STATS(ctx); s--)
        if ((Byte*)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart && order < p->MaxOrder)
            SetSuccessor(s, RemoveBinContexts(p, CTX(SUCCESSOR(s)), order + 1));
        else
            SetSuccessor(s, 0);

    return REF(ctx);
}
#endif

static UInt32 GetUsedMemory(const CPpmd8* p)
{
    UInt32 v = 0;
    unsigned i;
    for (i = 0; i < PPMD_NUM_INDEXES; i++)
        v += p->Stamps[i] * I2U(i);
    return p->Size - (UInt32)(p->HiUnit - p->LoUnit) - (UInt32)(p->UnitsStart - p->Text) - U2B(v);
}

#ifdef PPMD8_FREEZE_SUPPORT
    #define RESTORE_MODEL(c1, fSuccessor) RestoreModel(p, c1, fSuccessor)
#else
    #define RESTORE_MODEL(c1, fSuccessor) RestoreModel(p, c1)
#endif

static void RestoreModel(CPpmd8* p, CTX_PTR c1
#ifdef PPMD8_FREEZE_SUPPORT
                         , CTX_PTR fSuccessor
#endif
                         )
{
    CTX_PTR c;
    CPpmd_State* s;
    RESET_TEXT(0);
    for (c = p->MaxContext; c != c1; c = SUFFIX(c))
        if (--(c->NumStats) == 0)
        {
            s = STATS(c);
            c->Flags = (c->Flags & 0x10) + 0x08 * (s->Symbol >= 0x40);
            *ONE_STATE(c) = *s;
            SpecialFreeUnit(p, s);
            ONE_STATE(c)->Freq = (ONE_STATE(c)->Freq + 11) >> 3;
        }
        else
            Refresh(p, c, (c->NumStats + 3) >> 1, 0);

    for (; c != p->MinContext; c = SUFFIX(c))
        if (!c->NumStats)
            ONE_STATE(c)->Freq -= ONE_STATE(c)->Freq >> 1;
        else if ((c->SummFreq += 4) > 128 + 4 * c->NumStats)
            Refresh(p, c, (c->NumStats + 2) >> 1, 1);

    #ifdef PPMD8_FREEZE_SUPPORT
    if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
    {
        p->MaxContext = fSuccessor;
        p->GlueCount += !(p->Stamps[1] & 1);
    }
    else if (p->RestoreMethod == PPMD8_RESTORE_METHOD_FREEZE)
    {
        while (p->MaxContext->Suffix)
            p->MaxContext = SUFFIX(p->MaxContext);
        RemoveBinContexts(p, p->MaxContext, 0);
        p->RestoreMethod++;
        p->GlueCount = 0;
        p->OrderFall = p->MaxOrder;
    }
    else
    #endif
    if (p->RestoreMethod == PPMD8_RESTORE_METHOD_RESTART || GetUsedMemory(p) < (p->Size >> 1))
        RestartModel(p);
    else
    {
        while (p->MaxContext->Suffix)
            p->MaxContext = SUFFIX(p->MaxContext);
        do
        {
            CutOff(p, p->MaxContext, 0);
            ExpandTextArea(p);
        }
        while (GetUsedMemory(p) > 3 * (p->Size >> 2));
        p->GlueCount = 0;
        p->OrderFall = p->MaxOrder;
    }
}

static CTX_PTR CreateSuccessors(CPpmd8* p, Bool skip, CPpmd_State* s1, CTX_PTR c)
{
    CPpmd_State upState;
    Byte flags;
    CPpmd_Byte_Ref upBranch = (CPpmd_Byte_Ref)SUCCESSOR(p->FoundState);
    /* fixed over Shkarin's code. Maybe it could work without + 1 too. */
    CPpmd_State* ps[PPMD8_MAX_ORDER + 1];
    unsigned numPs = 0;

    if (!skip)
        ps[numPs++] = p->FoundState;

    while (c->Suffix)
    {
        CPpmd_Void_Ref successor;
        CPpmd_State* s;
        c = SUFFIX(c);
        if (s1)
        {
            s = s1;
            s1 = NULL;
        }
        else if (c->NumStats != 0)
        {
            for (s = STATS(c); s->Symbol != p->FoundState->Symbol; s++) ;
            if (s->Freq < MAX_FREQ - 9)
            {
                s->Freq++;
                c->SummFreq++;
            }
        }
        else
        {
            s = ONE_STATE(c);
            s->Freq += (!SUFFIX(c)->NumStats & (s->Freq < 24));
        }
        successor = SUCCESSOR(s);
        if (successor != upBranch)
        {
            c = CTX(successor);
            if (numPs == 0)
                return c;
            break;
        }
        ps[numPs++] = s;
    }

    upState.Symbol = *(const Byte*)Ppmd8_GetPtr(p, upBranch);
    SetSuccessor(&upState, upBranch + 1);
    flags = 0x10 * (p->FoundState->Symbol >= 0x40) + 0x08 * (upState.Symbol >= 0x40);

    if (c->NumStats == 0)
        upState.Freq = ONE_STATE(c)->Freq;
    else
    {
        UInt32 cf, s0;
        CPpmd_State* s;
        for (s = STATS(c); s->Symbol != upState.Symbol; s++) ;
        cf = s->Freq - 1;
        s0 = c->SummFreq - c->NumStats - cf;
        upState.Freq = (Byte)(1 + ((2 * cf <= s0) ? (5 * cf > s0) : ((cf + 2 * s0 - 3) / s0)));
    }

    do
    {
        /* Create Child */
        CTX_PTR c1; /* = AllocContext(p); */
        if (p->HiUnit != p->LoUnit)
            c1 = (CTX_PTR)(p->HiUnit -= UNIT_SIZE);
        else if (p->FreeList[0] != 0)
            c1 = (CTX_PTR)RemoveNode(p, 0);
        else
        {
            c1 = (CTX_PTR)AllocUnitsRare(p, 0);
            if (!c1)
                return NULL;
        }
        c1->NumStats = 0;
        c1->Flags = flags;
        *ONE_STATE(c1) = upState;
        c1->Suffix = REF(c);
        SetSuccessor(ps[--numPs], REF(c1));
        c = c1;
    }
    while (numPs != 0);

    return c;
}

static CTX_PTR ReduceOrder(CPpmd8* p, CPpmd_State* s1, CTX_PTR c)
{
    CPpmd_State* s = NULL;
    CTX_PTR c1 = c;
    CPpmd_Void_Ref upBranch = REF(p->Text);

    #ifdef PPMD8_FREEZE_SUPPORT
    /* The BUG in Shkarin's code was fixed: ps could overflow in CUT_OFF mode. */
    CPpmd_State* ps[PPMD8_MAX_ORDER + 1];
    unsigned numPs = 0;
    ps[numPs++] = p->FoundState;
    #endif

    SetSuccessor(p->FoundState, upBranch);
    p->OrderFall++;

    for (;;)
    {
        if (s1)
        {
            c = SUFFIX(c);
            s = s1;
            s1 = NULL;
        }
        else
        {
            if (!c->Suffix)
            {
                #ifdef PPMD8_FREEZE_SUPPORT
                if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
                {
                    do
                    {
                        SetSuccessor(ps[--numPs], REF(c));
                    }
                    while (numPs);
                    RESET_TEXT(1);
                    p->OrderFall = 1;
                }
                #endif
                return c;
            }
            c = SUFFIX(c);
            if (c->NumStats)
            {
                if ((s = STATS(c))->Symbol != p->FoundState->Symbol)
                    do
                    {
                        s++;
                    }
                    while (s->Symbol != p->FoundState->Symbol);
                if (s->Freq < MAX_FREQ - 9)
                {
                    s->Freq += 2;
                    c->SummFreq += 2;
                }
            }
            else
            {
                s = ONE_STATE(c);
                s->Freq += (s->Freq < 32);
            }
        }
        if (SUCCESSOR(s))
            break;
        #ifdef PPMD8_FREEZE_SUPPORT
        ps[numPs++] = s;
        #endif
        SetSuccessor(s, upBranch);
        p->OrderFall++;
    }

    #ifdef PPMD8_FREEZE_SUPPORT
    if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
    {
        c = CTX(SUCCESSOR(s));
        do
        {
            SetSuccessor(ps[--numPs], REF(c));
        }
        while (numPs);
        RESET_TEXT(1);
        p->OrderFall = 1;
        return c;
    }
    else
    #endif
    if (SUCCESSOR(s) <= upBranch)
    {
        CTX_PTR successor;
        CPpmd_State* s1 = p->FoundState;
        p->FoundState = s;

        successor = CreateSuccessors(p, False, NULL, c);
        if (successor == NULL)
            SetSuccessor(s, 0);
        else
            SetSuccessor(s, REF(successor));
        p->FoundState = s1;
    }

    if (p->OrderFall == 1 && c1 == p->MaxContext)
    {
        SetSuccessor(p->FoundState, SUCCESSOR(s));
        p->Text--;
    }
    if (SUCCESSOR(s) == 0)
        return NULL;
    return CTX(SUCCESSOR(s));
}

static void UpdateModel(CPpmd8* p)
{
    CPpmd_Void_Ref successor, fSuccessor = SUCCESSOR(p->FoundState);
    CTX_PTR c;
    unsigned s0, ns, fFreq = p->FoundState->Freq;
    Byte flag, fSymbol = p->FoundState->Symbol;
    CPpmd_State* s = NULL;

    if (p->FoundState->Freq < MAX_FREQ / 4 && p->MinContext->Suffix != 0)
    {
        c = SUFFIX(p->MinContext);

        if (c->NumStats == 0)
        {
            s = ONE_STATE(c);
            if (s->Freq < 32)
                s->Freq++;
        }
        else
        {
            s = STATS(c);
            if (s->Symbol != p->FoundState->Symbol)
            {
                do
                {
                    s++;
                }
                while (s->Symbol != p->FoundState->Symbol);
                if (s[0].Freq >= s[-1].Freq)
                {
                    SwapStates(&s[0], &s[-1]);
                    s--;
                }
            }
            if (s->Freq < MAX_FREQ - 9)
            {
                s->Freq += 2;
                c->SummFreq += 2;
            }
        }
    }

    c = p->MaxContext;
    if (p->OrderFall == 0 && fSuccessor)
    {
        CTX_PTR cs = CreateSuccessors(p, True, s, p->MinContext);
        if (cs == 0)
        {
            SetSuccessor(p->FoundState, 0);
            RESTORE_MODEL(c, CTX(fSuccessor));
        }
        else
        {
            SetSuccessor(p->FoundState, REF(cs));
            p->MaxContext = cs;
        }
        return;
    }

    *p->Text++ = p->FoundState->Symbol;
    successor = REF(p->Text);
    if (p->Text >= p->UnitsStart)
    {
        RESTORE_MODEL(c, CTX(fSuccessor)); /* check it */
        return;
    }

    if (!fSuccessor)
    {
        CTX_PTR cs = ReduceOrder(p, s, p->MinContext);
        if (cs == NULL)
        {
            RESTORE_MODEL(c, 0);
            return;
        }
        fSuccessor = REF(cs);
    }
    else if ((Byte*)Ppmd8_GetPtr(p, fSuccessor) < p->UnitsStart)
    {
        CTX_PTR cs = CreateSuccessors(p, False, s, p->MinContext);
        if (cs == NULL)
        {
            RESTORE_MODEL(c, 0);
            return;
        }
        fSuccessor = REF(cs);
    }

    if (--p->OrderFall == 0)
    {
        successor = fSuccessor;
        p->Text -= (p->MaxContext != p->MinContext);
    }
    #ifdef PPMD8_FREEZE_SUPPORT
    else if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
    {
        successor = fSuccessor;
        RESET_TEXT(0);
        p->OrderFall = 0;
    }
    #endif

    s0 = p->MinContext->SummFreq - (ns = p->MinContext->NumStats) - fFreq;
    flag = 0x08 * (fSymbol >= 0x40);

    for (; c != p->MinContext; c = SUFFIX(c))
    {
        unsigned ns1;
        UInt32 cf, sf;
        if ((ns1 = c->NumStats) != 0)
        {
            if ((ns1 & 1) != 0)
            {
                /* Expand for one UNIT */
                unsigned oldNU = (ns1 + 1) >> 1;
                unsigned i = U2I(oldNU);
                if (i != U2I(oldNU + 1))
                {
                    void* ptr = AllocUnits(p, i + 1);
                    void* oldPtr;
                    if (!ptr)
                    {
                        RESTORE_MODEL(c, CTX(fSuccessor));
                        return;
                    }
                    oldPtr = STATS(c);
                    MyMem12Cpy(ptr, oldPtr, oldNU);
                    InsertNode(p, oldPtr, i);
                    c->Stats = STATS_REF(ptr);
                }
            }
            c->SummFreq = (UInt16)(c->SummFreq + (3 * ns1 + 1 < ns));
        }
        else
        {
            CPpmd_State* s = (CPpmd_State*)AllocUnits(p, 0);
            if (!s)
            {
                RESTORE_MODEL(c, CTX(fSuccessor));
                return;
            }
            *s = *ONE_STATE(c);
            c->Stats = REF(s);
            if (s->Freq < MAX_FREQ / 4 - 1)
                s->Freq <<= 1;
            else
                s->Freq = MAX_FREQ - 4;
            c->SummFreq = (UInt16)(s->Freq + p->InitEsc + (ns > 2));
        }
        cf = 2 * fFreq * (c->SummFreq + 6);
        sf = (UInt32)s0 + c->SummFreq;
        if (cf < 6 * sf)
        {
            cf = 1 + (cf > sf) + (cf >= 4 * sf);
            c->SummFreq += 4;
        }
        else
        {
            cf = 4 + (cf > 9 * sf) + (cf > 12 * sf) + (cf > 15 * sf);
            c->SummFreq = (UInt16)(c->SummFreq + cf);
        }
        {
            CPpmd_State* s = STATS(c) + ns1 + 1;
            SetSuccessor(s, successor);
            s->Symbol = fSymbol;
            s->Freq = (Byte)cf;
            c->Flags |= flag;
            c->NumStats = (Byte)(ns1 + 1);
        }
    }
    p->MaxContext = p->MinContext = CTX(fSuccessor);
}

static void Rescale(CPpmd8* p)
{
    unsigned i, adder, sumFreq, escFreq;
    CPpmd_State* stats = STATS(p->MinContext);
    CPpmd_State* s = p->FoundState;
    {
        CPpmd_State tmp = *s;
        for (; s != stats; s--)
            s[0] = s[-1];
        *s = tmp;
    }
    escFreq = p->MinContext->SummFreq - s->Freq;
    s->Freq += 4;
    adder = (p->OrderFall != 0
             #ifdef PPMD8_FREEZE_SUPPORT
             || p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE
             #endif
             );
    s->Freq = (Byte)((s->Freq + adder) >> 1);
    sumFreq = s->Freq;

    i = p->MinContext->NumStats;
    do
    {
        escFreq -= (++s)->Freq;
        s->Freq = (Byte)((s->Freq + adder) >> 1);
        sumFreq += s->Freq;
        if (s[0].Freq > s[-1].Freq)
        {
            CPpmd_State* s1 = s;
            CPpmd_State tmp = *s1;
            do
                s1[0] = s1[-1];
            while (--s1 != stats && tmp.Freq > s1[-1].Freq);
            *s1 = tmp;
        }
    }
    while (--i);

    if (s->Freq == 0)
    {
        unsigned numStats = p->MinContext->NumStats;
        unsigned n0, n1;
        do
        {
            i++;
        }
        while ((--s)->Freq == 0);
        escFreq += i;
        p->MinContext->NumStats = (Byte)(p->MinContext->NumStats - i);
        if (p->MinContext->NumStats == 0)
        {
            CPpmd_State tmp = *stats;
            tmp.Freq = (Byte)((2 * tmp.Freq + escFreq - 1) / escFreq);
            if (tmp.Freq > MAX_FREQ / 3)
                tmp.Freq = MAX_FREQ / 3;
            InsertNode(p, stats, U2I((numStats + 2) >> 1));
            p->MinContext->Flags = (p->MinContext->Flags & 0x10) + 0x08 * (tmp.Symbol >= 0x40);
            *(p->FoundState = ONE_STATE(p->MinContext)) = tmp;
            return;
        }
        n0 = (numStats + 2) >> 1;
        n1 = (p->MinContext->NumStats + 2) >> 1;
        if (n0 != n1)
            p->MinContext->Stats = STATS_REF(ShrinkUnits(p, stats, n0, n1));
        p->MinContext->Flags &= ~0x08;
        p->MinContext->Flags |= 0x08 * ((s = STATS(p->MinContext))->Symbol >= 0x40);
        i = p->MinContext->NumStats;
        do
        {
            p->MinContext->Flags |= 0x08 * ((++s)->Symbol >= 0x40);
        }
        while (--i);
    }
    p->MinContext->SummFreq = (UInt16)(sumFreq + escFreq - (escFreq >> 1));
    p->MinContext->Flags |= 0x4;
    p->FoundState = STATS(p->MinContext);
}

CPpmd_See * Ppmd8_MakeEscFreq(CPpmd8* p, unsigned numMasked1, UInt32* escFreq)
{
    CPpmd_See* see;
    if (p->MinContext->NumStats != 0xFF)
    {
        see = p->See[p->NS2Indx[p->MinContext->NumStats + 2] - 3] +
              (p->MinContext->SummFreq > 11 * ((unsigned)p->MinContext->NumStats + 1)) +
              2 * (2 * (unsigned)p->MinContext->NumStats <
                   ((unsigned)SUFFIX(p->MinContext)->NumStats + numMasked1)) +
              p->MinContext->Flags;
        {
            unsigned r = (see->Summ >> see->Shift);
            see->Summ = (UInt16)(see->Summ - r);
            *escFreq = r + (r == 0);
        }
    }
    else
    {
        see = &p->DummySee;
        *escFreq = 1;
    }
    return see;
}

static void NextContext(CPpmd8* p)
{
    CTX_PTR c = CTX(SUCCESSOR(p->FoundState));
    if (p->OrderFall == 0 && (Byte*)c >= p->UnitsStart)
        p->MinContext = p->MaxContext = c;
    else
    {
        UpdateModel(p);
        p->MinContext = p->MaxContext;
    }
}

void Ppmd8_Update1(CPpmd8* p)
{
    CPpmd_State* s = p->FoundState;
    s->Freq += 4;
    p->MinContext->SummFreq += 4;
    if (s[0].Freq > s[-1].Freq)
    {
        SwapStates(&s[0], &s[-1]);
        p->FoundState = --s;
        if (s->Freq > MAX_FREQ)
            Rescale(p);
    }
    NextContext(p);
}

void Ppmd8_Update1_0(CPpmd8* p)
{
    p->PrevSuccess = (2 * p->FoundState->Freq >= p->MinContext->SummFreq);
    p->RunLength += p->PrevSuccess;
    p->MinContext->SummFreq += 4;
    if ((p->FoundState->Freq += 4) > MAX_FREQ)
        Rescale(p);
    NextContext(p);
}

void Ppmd8_UpdateBin(CPpmd8* p)
{
    p->FoundState->Freq = (Byte)(p->FoundState->Freq + (p->FoundState->Freq < 196));
    p->PrevSuccess = 1;
    p->RunLength++;
    NextContext(p);
}

void Ppmd8_Update2(CPpmd8* p)
{
    p->MinContext->SummFreq += 4;
    if ((p->FoundState->Freq += 4) > MAX_FREQ)
        Rescale(p);
    p->RunLength = p->InitRL;
    UpdateModel(p);
    p->MinContext = p->MaxContext;
}

/* H->I changes:
   NS2Indx
   GlewCount, and Glue method
   BinSum
   See / EscFreq
   CreateSuccessors updates more suffix contexts
   UpdateModel consts.
   PrevSuccess Update
 */